It is often desirable to combine soap together with synthetic surfactant (specifically chips comprising acyl isethionate, free fatty acid and alkali metal isethionate, typically such chips are made from the direct esterification of free fatty acids and alkali metal isethionates to form so-called "DEFI"--directly esterified fatty acid isethionate-chips). For example, adding soap to "DEFI" chips or flakes noted above reduces cost (soap being much cheaper), while adding such chips or flakes to a predominantly soap composition reduces harshness of soaps. However, mixing such "DEFI" flakes or chips with soap in a conventional process results in bars with high degree of "grittiness". Thus it has been traditionally true that combining too much soap with such chips or flakes, or adding too much chips or flakes to predominantly soap bars has resulted (when chips or flakes are co-extruded with soap chips) in bars having poor user properties. Without wishing to be bound by theory, this is believed to be caused by differences in wear rates between the chips or flakes comprising acyl isethionate and the soap chips thereby resulting in the so-called "grittiness" problem.
One method of alleviating this problem has been to use a molten process. Thus, for example, it is possible to mix much higher percentages of acyl isethionate based chips or flakes with soap chips by using a molten process in which relatively high amounts of water (i.e., 12% to 18% by wt.) are mixed with the soap and surfactant to ensure sufficient surfactant mixing after which the mixture is heated and the water removed to about 5% water (e.g., by vacuum or spray drying). The process is far more complicated, time-consuming and expensive than a non-molten process.
Unexpectedly, applicants have found that if, rather than using so-called DEFI-type chips taken directly from the esterification reaction vessel, the DEFI chip is processed further (e.g., by blending the DEFI chip with additional fatty acids, fatty acid soaps, additional surfactant such as betaine, and minors as if to form a final synthetic bar comprising soap, fatty acid and DEFI), this "pre-processed" chip can be combined with soap chips and result in significant reduction in grit of the final bars. Moreover, the preprocessed isethionate chips and soap chips can be blended in a non-molten process.
Preprocessing essentially involves blending of the "DEFI" solid (i.e., solid resulting from reaction of alkali metal isethionate and fatty acids) with fatty acid soap (e.g., blends of coconut and tallow soaps and/or alkali metal stearate), optional surfactant (e.g., betaine)and other minor components using the same process as that used to manufacture final soap (e.g., mixing component at greater than 90.degree. C. for at least 15 minutes, cooling, for example on a chill roll and refining to form chips). This raw material so formed (without colorant, perfume) is collected in the form of noodles or chips, and then used as the Na acyl isethionate source in the current non-molten process. In this diluted and processed form, the crystallinity of the Na acyl isethionate solid is believed to be significantly reduced. This in turn is believed to greatly facilitate blending of this material into the final bar solid, which drastically reduces the occurrence of grit upon washing.
In another embodiment of the invention, grit is reduced even further by using filler in addition to preprocessed Isethionate chip flake and soap chip. Without being bound by theory, it is believed that filler acts to both aid in dispersion of the Na acyl isethionate and soap solids in the mixing process, via a grinding action, and as a diluent which makes any grit particulates less noticeable.
The art teaches manufacture of bars which are non-gritty. WO 94/26866 to Chambers, for example, teaches mixing fatty isethionate ester with soap to form bars. This is clearly, however, a process requiring isotropic solution and not a non-molten process. Further, there is nothing about pre-processing the acyl Isethionate source.
EP 434,460 to Lee et al. (Unilever) teaches soap and isethionate compositions. The soaps are made using 5 to 50% water and organic solvents and are clearly not non-molten. Also, there is again nothing about pre-processing.
U.S. Pat. No. 5,494,612 to Finucane teaches a process for producing bars comprising isethionate and soap. Although the composition may be dry-mixed (see column 7, lines 46-49), the composition must comprise less than 5% soap. If higher amounts are used in a dry-mix process, the grittiness issues resurfaces. There is also nothing about pre-processing.
Accordingly, it is an object of the invention to provide a non-molten mix process wherein a broad range of soap and acyl isethionate may be mixed without providing grittiness.